From driscoll@curacao.dartmouth.edu Mon Dec 12 12:33 CST 1994
Date: Mon, 12 Dec 1994 13:31:01 -0500
From: driscoll@curacao.dartmouth.edu (Jim Driscoll)
Message-Id: <199412121831.NAA05226@curacao.dartmouth.edu>
To: winstead@cs.tulane.edu
Subject: hi
Content-Type: text
Content-Length: 4513

How goes your fermenter project?  I saw your query about inexpensive
TIG rigs, but I don't know anything about them.  I can tell you that
as my welding skills have improved, I increasingly appreciated the
Miller Synchrowave that I purchased.  It is not cheap, however.  I
notice that your email address is from a university.  Most have a
metal shop somewhere and it is often thae case that students and
faculty can use it.  It is also usually staffed by very skilled people
who usually like beer.

I also saw your request trying to locate me; I am that gentleman
building a brewery.  Enclosed below is the initial response I sent in
response to your request for info about sanitary welding.  If you make
it available to the homebrewing groups, I would appreciate
attribution: after all, they are potential customers :-].

I live fairly close to Newark airpost.  Should your travel plans have
you flying through, and you can arrange a sufficiently long layover,
and you have the interest, I can show you my shop and some things I
have built.

Here is the initial post:

I have been unable to find any book on sanitary welding.  If you do
find something of that sort I would appreciate hearing about it.

Your post didn't give much of a clue as to your knowledge of metal
fabrication, so here goes an explanation that may or may not be
optimally intelligible or useful:

The material I use is type 304, but some prefer 304L for increased
weldability.  I am usually using 12ga, but for a homebrew setup 18ga
is about as thin as I would go to still be easily weldable.  For this
gauge, the mill finish, 2B, should be sufficient for homebrewing, but
you can get a #3 or better yet a #4 finish for the inside if you are
feeling generous.  I would recommend getting the material with
removable protective coating for the inside that will protect the finish
while you build the equipment.  You can cut it away from joints with a
home-made copper blade made by grinding a squashed piece of copper
tube.

Never let anything made of mild steel touch your stainless, and
don't use anything that has touched mild steel on it either (e.g. a
grinding wheel).

The welding method of choice is TIG or GTAW.  Be scrupulous about your
tungsten!  always grind it to a point on a grinding wheel reserved for
only tungsten, and if it it touches the weld puddle immediately cut
off and regrind the tip.


I butt weld joints.  For tanks tack weld the compennents into position
with as close a fitup as possible--it is worth the trouble.  I use
hydraulic spreaders and cargo load straps to bring things into
position/into round.  I then weld the inside with filler rod,
penetrating say 2/3 of the joint, then weld the outside with filler.
I am moving toward backing the joint on the outside with flux or a
consumable weld backing material and then making one pass on the
interior.  Alternatively, you could back it with inert gas, but this
won't support the weld puddle.

After welding I use what I think are called polifan wheels from Pferd
abrasives mounted on an angle grinder to grind/finish the weld on the
interior.  To get a better finish I use flap wheels or non-woven nylon
abrasive wheels mounted on a straight grinder afterwards.  After this
has been done, the weld should not be visible, there sould be no pits
or high spots.  About the only thing you should be able to detect is
a difference in finish in the area of the weld.

For a really fine finish you can send the finished assembly to an
elecropolisher, but unless you are Coors, this is usally reserved only
for yeast propagation plants.

Now here comes the tricky part.  Most people will tell you that you
must passivate the heat affected zone, by which they mean that the
free iron brought to the surface by the welding process is removed and
the protective chromium oxide layer is restored.  My experience is
that if the heat affected zone is finished well with suitable
asbrasive materials the joint will not corrode.  For your purposes you
can probably use it as finished, and if you note any corrosion, it can
be removed with the green hand pads sold at your local grocery store
for dishwashing.  If you insist on passivating it, I can tell you how
it can be done, but it requires using dangerous acids.

You should be aware that "fresh" stainless steel has a taste.  When
commercial brewers bring a new piece of equipment on-line, they first
fill it with finished beer, let it sit a bit, and then discard the
beer.

	Good luck,

	Jim Driscoll
	Driscoll Brewing